In these small hours

It occurs to me that cinema has so far done a poor job of capturing those inside jokes that exist between spouses, and I can't figure out why.

Occasionally textual writers give us a believable glimpse of these small moments:

• The quizzical look that means something precise and discernible only to two people.
• The repeated word or words that become part of our daily dialogue and would be impossible to explain fully to outsiders. SGF and I could get by on nothing but these known phrases -- inside jokes accumulated during our relatively short time together -- for an alarming length of time without any lapse in understanding. Most observers would be completely bewildered, of course.
• The silly fictional character borne of a silly moment watching TV together, who revisits one's household as circumstances dictate.
• The "pet voice" that communicates so much -- commentary on the parents' choice of the spicy salmon roll over the spicy tuna roll, the temperature or noise level in the home, the merits of turkey florentine over any other kind of florentine, what's on the parents' DVR list, how they've chosen to decorate the bedroom, etc. SGF and I aren't the only ones who know this voice well, and yet I rarely see/hear it on television or on the big screen.

Why do these small but telling facets of our lives escape depiction in film, a medium that seems so well suited to laying out life as it really is? Is it that life as it really is -- unfailingly hilarious to us on the family level -- is actually far too nuanced or too boring or too difficult to explain for mass consumption?